Postage meters are mass produced devices for printing a defined unit value for governmental or private carrier delivery of parcels and envelopes. The term postage meter also includes other like devices which provide unit value printing such as tax stamp meters. Postage meters include internal accounting devices which account for postage value representation which is stored within the meter and is printed by the meter. As a result, postage meters must possess an extremely high reliability to avoid the loss of user or government funds stored within the meter.
Electronic postage meters have been developed with electronic accounting circuitry. Postage meter systems of this type are disclosed in U.S. Pat. No. 3,978,457 for MICROCOMPUTERIZED ELECTRONIC POSTAGE METER SYSTEM; and U.S. Pat. No. 4,301,507 for ELECTRONIC POSTAGE METER HAVING PLURAL COMPUTING SYSTEM. The electronic accounting circuits of the meter include non-volatile memory capability for storing postage accounting information. The memory function in the electronic accounting circuits have replaced the function served in mechanical postage meters by mechanical accounting registers. The non-volatile memory and value selection in the electronic postage meters of the aforementioned patents, as well as other meter functions, are operated under microcomputer control.
Postage meters with mechanical accounting registers are not subject to many of the problems encountered by electronic postage meters. Conditions cannot normally occur in postage meters with mechanical registers that prevent, for example, accounting for a printing cycle or which will result in the loss of data stored in the mechanical registers. This is not the case with electronic postage meters. Electronic postage meters are subject to the effects of electromagnetic radiation which can effect their operation. Thus, precautions must be taken, as for example by proper shielding, to protect the meter's electronic components from the effects of electromagnetic radiation. Mechanical security must, of course, also be provided. It has been recognized that it is desirable to energize electronic postage meters in a manner which eliminates or minimizes the problems associated with electromagnetic radiation. For example, a power supply wherein only the secondary winding is within the meter secure structure is disclosed in U.S. Patent Application Ser. No. 344,651, now Pat. No. 4,471,440, filed Feb. 1, 1982, by Frank T. Check, Jr. for ELECTRONIC POSTAGE METER HAVING POWER MAGNETICALLY COUPLED TO THE METER FROM THE METER BASE. Also, the need for efficient power supplies in electronic postage meters is noted in U.S. Patent Application Ser. No. 306,805, now Pat. No. 4,472,781, filed Sept. 29, 1981, by Roland G. Miller for Power Supply System. Both applications are assigned to Pitney Bowes Inc.